In a scroll machine such as a pump, compressor or expander, there is one basic coaction between the scroll elements in that one must orbit with respect to the other. In the case of a compressor, the fluid being compressed exerts a force on the scroll elements tending to separate them axially and to radially separate the wraps of the scroll elements. To achieve the necessary sealing for compressor operation some form of axial and radial compliance are required. Axial compliance may take the form of discharge or intermediate pressure acting on the plate of the orbiting scroll so as to bias the tips of the wrap of the orbiting scroll into engagement with the floor of the fixed scroll. Another form of axial compliance is the tip seal which is located in a groove in the wrap tip. A tip seal may also be used to avoid contact between the tip of the wrap of one scroll element and the floor of the facing scroll element.
Inertia considerations may sometimes dictate that the orbiting scroll be as lightweight as possible. Based upon a weight consideration, aluminum is a desirable material for the orbiting scroll. Wear characteristics of aluminum may dictate the use of a tip seal to avoid wear of the tip of the wrap as well as to avoid seizure. Because of the machining requirements for the groove to receive the tip seal and leakage problems associated with the use of a tip seal, it is generally preferred to avoid the use of a tip seal. However, the use of aluminum scroll elements without tip seals has been unsatisfactory in the prior art.